1. Field of the Invention
The invention relates to finishing the surface of workpiece and, more specifically, to finishing the surface of a workpiece using a laser.
2. Description of the Related Art
In the automotive industry, certain vehicle parts, such as a rear deck air spoiler, are made of plastic. Since these parts are generally exterior parts, surface quality or finish is critical. Even when the part is an interior part, surface finish is important. However, these vehicle parts are formed by a variety of techniques providing various surface qualities, such techniques including blow molding, injection molding, extrusion, etc. Many of these techniques provide a surface requiring labor and sanding to meet surface requirement standards. In particular, for example, a blow molding process produces a part requiring extensive labor and sanding to meet class A surface requirements. This is expensive and increases the part cost.
What is needed is an apparatus and method that is capable of finishing the surface of a vehicle part to meeting class A surface finish requirements while minimizing the need for manual sanding.
The invention is an apparatus and method for finishing the surface of a vehicle part using a laser. The method of the invention comprises the steps of: measuring a first height of a footprint area of the surface, comparing the first height to a reference height associated with the footprint area; and firing a laser onto the footprint area when the first height is above the reference height. Preferably, the surface includes a plurality of footprint areas, and these steps are performed for each footprint area of the surface in a predetermined pattern. In one aspect of the invention, the steps are performed by dividing the surface into sets of footprint areas, each set including a predetermined number of footprint areas; and repeating the steps for a set of footprint areas until the laser is not fired at any footprint area in the set. Then, the invention proceeds to repeat the steps for the next set of footprint areas until the steps are performed for all the sets.
In another aspect of the invention, the method further comprises the steps of measuring a second height of the footprint area after the firing step and comparing the second height to the reference height associated with the footprint area. All of the steps are completed at least once for each footprint area. In one aspect, the steps are repeated for each footprint area if the step of comparing the second height shows that the second height of each footprint area is above the reference height associated with each footprint area.
The apparatus of the present invention comprises: means for measuring a first height of a footprint area of the surface, means for comparing the first height to a reference height associated with the footprint area; and means for firing a laser onto the footprint area when the first height is above the reference height. In another aspect of the invention, the apparatus further comprises means for measuring a second height of the footprint area after the firing step, and means for comparing the second height to the reference height associated with the footprint area. In one aspect of the invention, the size of the footprints are determined based on the energy density of the laser.
Preferably, the means for measuring the first height is a first surface topography sensor, and the means for measuring the second height is a second surface topography sensor. The reference height for each footprint area is a math data coordinate corresponding to a design data point of the surface.
In one aspect of the invention, the laser is a pulsed laser. In another aspect, the laser is a continuous output laser.
Thus, the invention provides an apparatus and method for finishing the surface of a vehicle part using a laser, which minimizes manual sanding.